Plummeting numbers of people leaving the UK to live abroad and the influx of migrants from Eastern Europe led to a 21% increase in net migration last year, figures have revealed.

The number of people coming to the UK for more than a year, less the number leaving, hit 239,000, the second highest annual figure on record and the fourth highest figure for any 12-month period since records began.

Analysts and campaigners said it would make it "more difficult than ever" for the Government to fulfil its pledge to cut net migration to the tens of thousands by 2015.

The Government has no control over those leaving the UK and long-term emigration fell from 427,000 in 2008 to 336,000 last year, showed estimates from the Office for National Statistics (ONS).

Long-term immigration remained constant overall at about 575,000, but the number of Poles and other eastern Europeans coming to the UK continued to rise.

Net migration from the so-called A8 countries which joined the EU in May 2004 - Poland, the Czech Republic, Hungary, Slovakia, Slovenia, Estonia, Latvia and Lithuania - rose almost eight-fold last year to 39,000 from 5,000 in 2009, said the ONS.

A record 241,000 migrants also settled permanently in the UK last year, largely because tens of thousands of asylum seekers whose cases were in a backlog were allowed to stay.

Immigration Minister Damian Green said the rise in net migration covered a period before the Government's immigration reforms were brought in.

"After almost two years of increasing net migration the figures stabilised in the last quarter," he said. "This explains why the Government radically changed immigration policy, from our first months in office, to drive the numbers down with a limit on economic migration and changes to student visas to ensure we attract the brightest and best whilst tackling widespread abuse of the system."

The increase to 239,000 from 198,000 in 2009 was the second highest year-end figure since records began in 1991, behind 245,000 in December 2004, but it was down slightly from 242,000 in the 12-months to September 2010. It was also the fourth highest figure for any 12-month period on record, behind 260,000 in the year ending June 2005, 245,000 in the year ending December 2004, and 242,000 in the year ending September 2010.